The present invention relates to scintigram display apparatus provided with multilevel analyzer that makes easy and precise the analysis of scan data gotten by an isocount scintillation scanner. A scintigram display apparatus with two-dimensional interpolation which allows composition of a high quality scintigram within short scanning time is also described.
In the isocount scintiscanning, the detector probe is moved rectilinearly within the limit switches and within a plane over the object under examination. At each observation point, the time T necessary for the radiation to reach a preset value N is measured. From said values N and T, the count rate R = N/T is calculated electronically and a set of two-dimensional array of count rate R.sub.i,j (i = 1, 2 . . . , m; j = 1, 2 . . . , n) corresponding to each picture element is gathered as data.
A widely used recording and displaying means of said data has been the photographic film. In a photoscintigram the two-dimensional array of R.sub.i,j is recorded on the film as a picture element with density proportional to R.sub.i,j. The diagnosis is based on said picture constituted by variation of gray scale level. It is known, however, that the human eye can distinguish at most ten different levels on a monochromatic film, a very low perception ability. On the other hand, some very unstable parameters such as the adjustment of light source intensity and film developing conditions makes the diagnosis based on monochromatic film somewhat unstable and with poor reliability.
On the other hand, in the isocount scintiscan, the data are normally taken 3 mm apart, for instance, and each picture element is a square 3 mm .times. 3 mm. If the measurements are taken 6 mm apart and the present value maintained the same N, the observing time may be reduced to about 1/4. Even considering the time necessary for moving the detector probe and the scanning of background region, the entire measuring time may be considerably reduced. However, if the picture element size was taken to be 6 mm square, the resulting scintigram should be rough and constitute an embarrassment in its interpretation.
This invention aims at alleviating the above mentioned difficulties and prevents a display apparatus that enables a stable composition of scintigrams in an easily interpreted form through multilever analyzer. Another objective of this invention is to present a display system that shortens the scanning time by composing a scintigram with 3 mm .times. 3 mm picture elements, for instance, from data taken 6 mm apart, through two-dimensional interpolation. This process yields an improved picture quality without any loss of details.
In order to achieve these goals, the count rate R.sub.i,j distributed in a two-dimensional array, gathered by the isocount method, are read in the memory in the same sequence that they are taken. Then, R.sub.11, R.sub.12 . . . . R.sub.1n ; R.sub.21, R.sub.22 . . . , R.sub.2n, etc. are read out in that order, in synchronism with the television horizontal sweep signal. If R.sub.ij is larger than or equal to a certain slice level a.sub.k (R.sub.ij .gtoreq. a.sub.k), black is assigned to the corresponding element; if R.sub.ij is smaller than the slice level a.sub.k (R.sub.ij &lt; a.sub.k), white is assigned to that element and displayed on the screen. By this means, a kind of silhouette corresponding to a section of scan data at said slice level a.sub.k is seen on the television screen. If said level a.sub.k is changed sequentially at a suitable speed, the silhouette gets movement by changing it form. Human sensors are very sensitive to variations, particularly the eye, and this procedure makes the feature extraction from the scintigram very easy.
On the other hand, a two-dimensional interpolation that allows display of 3 mm square pictures elements from data taken 6 mm apart is also presented in this invention and is based on the following principle. The object plane should be constituted by small square picture elements regularly distributed. The measurements are made at the intersections of odd numbered horizontal lines with odd numbered vertical lines that constitute the boundary of said picture elements. The count rate of each picture element is determined by the nearest three measurements in the following fashion: a column of height X.sub.ij, the result of measurement, is placed at each measuring point; a plane is determined by said three nearest columns; the height up to this plane at the center of each picture element is adopted as the value of its count rate. The scanning time may be reduced considerably by this means, without deterioration of picture quality.
Other objectives, chacteristics, effects, and more details are described by the drawings and explanation of the preferred embodiments.